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Biodegradation in water: screening tests

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Endpoint:
biodegradation in water: ready biodegradability
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Acceptable well documented report; Study conducted according to guideline in compliance with GLP; Read-across substance used.
Qualifier:
according to
Guideline:
EU Method C.4-E (Determination of the "Ready" Biodegradability - Closed Bottle Test)
Version / remarks:
Cited as Directive 92/69/EEC, C.4-E
GLP compliance:
not specified
Oxygen conditions:
aerobic
Inoculum or test system:
other: secondary effluent of a municipal sewage plant (Breisgauer Bucht, 500000 population equivalent), 0.4 mL/L
Duration of test (contact time):
28 d
Initial conc.:
3 mg/L
Based on:
test mat.
Reference substance:
acetic acid, sodium salt
Key result
Parameter:
other: ThOD
Remarks:
Theoretical Oxygen Demand
Value:
89
Sampling time:
28 d
Details on results:
Blanks:

Maximum deviation between parallels = 8.9%
Oxygen consumption after 28 days = 0.79-1.18 mg/L
pH : 7.2 at the beginning and 6.7 at the end of the test

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Sodium gluconate:

Maximum deviation between parallels = 4.6% at day 3
Biological degradation : 61% of ThOD after 3 days
Maximum degradation = 89% of the ThOD at day 28
pH : 7.2 at the beginning and 6.7 at the end of the test

Oxygen concentration during test never felt below 5.9 mg/lL.
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Reference item (sodium acetate):

Maximum deviation between parallels = 3.8% at day 14.
Biological degradation : 67% after 3 days
pH : 7.2 at the beginning and 6.7 at the end of the test

Kinetic of test substance (in %):
= 61.13 after 3 day(s)
= 74.35 after 7 day(s)
= 66.09 after 14 day(s)
= 71.94 after 21 day(s)
= 88.88 after 28 day(s)

Kinetic of control substance (in %):
= 67.15 after 3 day(s)
= 80.93 after 28 day(s)
Degradation products: not measured

The 89% degradation indicated here relates to the Theoritical Oxygen Demand (ThOD).

Validity criteria fulfilled:
yes
Remarks:
Oxygen depletion in the inoculum blank did not exceed 1.5 mg dissolved oxygen/litre after 28 days.
Interpretation of results:
readily biodegradable
Conclusions:
The read-across substance sodium gluconate (CAS 527-07-1) is readily biodegradable with 89% degradation (based on ThOD) after 28 days. Conclusively, the target substance is also considered as readily biodegradable.
Executive summary:

The biodegradation of the test substance sodium gluconate (CAS 527-07-1) was investigated according to EU Method C.4-E (Closed bottle test) in compliance with GLP (Hydrotox GmbH, 2001; as cited in OECD SIDS, 2004).

All in all, 16 test bottles with a test item concentration of 3 mg/L with 4 mL/L inoculum (secondary effluent of a municipal sewage plant) were filled bubble-free and incubated in the dark at 20°C for 28 days. On days 3, 7, 10, 14, 21 and 28, at least duplicate bottles were removed for determination of dissolved oxygen and pH. At the end of the test, dissolved oxygen concentration in all remaining bottles was measured. Reference item bottles containing sodium acetate stock solution (concentration= 4 mg/L) with 0.4 mL/L inoculum were also filled and incubated in the dark at 20°C. A blank was also prepared without any stock solution.

Referring to the test substance and based on the ThOD, 61.13% degradation were reported after 3 days, followed by 74.35% after 7 days, 66.09% after 14 days, 71.94% after 21 days and 88.88% after 28 days. With regard to the reference substance, 67.15% degradation were measured after 3 days and 80.93% after 28 days – both based on the ThOD.

Endpoint:
biodegradation in water: screening tests
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Study conducted according to guideline in compliance with GLP; Acceptable well documented report; Read-across substance used.
Qualifier:
according to
Guideline:
other: DIN EN ISO 11734
GLP compliance:
not specified
Oxygen conditions:
anaerobic
Inoculum or test system:
other: Digesting sludge of a municipal sewage plant (Breisgauer Bucht, 500000 population equivalent), 2.9 g total solids/L
Duration of test (contact time):
35 d
Initial conc.:
303 mg/L
Based on:
test mat.
Reference substance:
benzoic acid, sodium salt
Value:
100
Sampling time:
35 d
Details on results:
Test item:
The percentage biodegradation is calculated from the total carbon transformed to biogas and DIC and the measured or calculated amount of carbon added as test item. The test item was degraded to 50% by day 8 and to 66% by day 35.

The summing up of the net-mass carbon in the liquor shows that the test item is completely anaerobically degraded after 35 days.

The pH at the end of the test was 6.8 in every bottle.
Bottles with blanks showed a pH of 7.1-7.2.

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Reference (sodium benzoate) :
The degradation of the reference item took some time to get started. Between days 18 and 22 this lag-phase was over and the curve reached 67% by day 35. After considering the DIC in the liquor, the reference item was also anaerobically degraded completely in 35 days. The pH at the end of the test was 6.8 in every bottle.

Kinetic of test substance (in %):
= 8 after 1 day(s)
= 51 after 8 day(s)
= 57 after 15 day(s)
= 61 after 22 day(s)
= 100 after 35 day(s)

Kinetic of control substance (in %):
= 6 after 8 day(s)
= 100 after 35 day(s)
Degradation products: not measured

At day 35, the average degradation percentage is 66% but the value shown includes the dissolved inorganic carbon (DIC).

Validity criteria fulfilled:
not specified
Interpretation of results:
other: The test item is ultimately biodegradable under anaerob test conditions.
Conclusions:
The test substance Sodium gluconate (CAS 527-07-1) is ultimately biodegradable under anaerobic test conditions.
Executive summary:

The biodegradation of the test substance Sodium gluconate (CAS 527-07-1) was investigated according to DIN EN ISO 11734 in compliance with GLP (Hydrotox GmbH, 2001; as cited in OECD SIDS, 2004).

Washed digested sludge containing very low amounts of inorganic carbon (IC) was diluted to 1-3 g/L total solids concentration and incubated in the absence of oxygen at 35 +/-2°C in sealed vessels with the test item (303 mg/L) at a concentration of 20-200 mg/L total organic carbon (TOC) for 35 days. As reference substance, sodium benzoate (0.069 g/400 mL) has been used. The percentage biodegradation is calculated from the total carbon transformed to biogas and DIC and the measured or calculated amount of carbon added as test item.

Referring to the test substance, 8% degradation has been determined after 1 day, followed by 51% after 8 days, 57% after 15 days, 61% after 22 days and 100% after 35 days. With regard to the reference substance, 6% degradation was determined after 8 days and 100% after 35 days.

Description of key information

Sodium gluconate_EU Method C.4-E: 89 % degradation after 28 days
Sodium gluconate_DIN EN ISO 11734: 100 % after 35 days (anaerobic)

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

Two experimental study reports are cited in the OECD SIDS Report (2004) on Gluconic Acid and its Derivatives. Both studies refer to the read-across substance Sodium gluconate (CAS 527 -07 -01). Actual data on the target substance Calcium glucoheptonate is not available for this endpoint. Nevertheless, conclusions drawn on the read-across substance are assignable for the target substance as well (please refer to read-across statement).

Referring to the key study, the biodegradation of sodium gluconate (CAS 527-07-1) was investigated according to EU Method C.4-E (Closed bottle test) in compliance with GLP (Hydrotox GmbH, 2001; as cited in OECD SIDS, 2004).

All in all, 16 test bottles with a test item concentration of 3 mg/L with 4 mL/L inoculum (secondary effluent of a municipal sewage plant) were filled bubble-free and incubated in the dark at 20°C for 28 days. On days 3, 7, 10, 14, 21 and 28, at least duplicate bottles were removed for determination of dissolved oxygen and pH. At the end of the test, dissolved oxygen concentration in all remaining bottles was measured. Reference item bottles containing sodium acetate stock solution (concentration= 4 mg/L) with 0.4 mL/L inoculum were also filled and incubated in the dark at 20°C. A blank was also prepared without any stock solution.

Referring to the test substance and based on the ThOD, 61.13% degradation were reported after 3 days, followed by 74.35% after 7 days, 66.09% after 14 days, 71.94% after 21 days and 88.88% after 28 days. With regard to the reference substance, 67.15% degradation were measured after 3 days and 80.93% after 28 days – both based on the ThOD.

With regard to the supporting information, the biodegradation of sodium gluconate (CAS 527-07-1) was investigated according to DIN EN ISO 11734 in compliance with GLP (Hydrotox GmbH, 2001; as cited in OECD SIDS, 2004).

Washed digested sludge containing very low amounts of inorganic carbon (IC) was diluted to 1-3 g/L total solids concentration and incubated in the absence of oxygen at 35 +/-2°C in sealed vessels with the test item (303 mg/L) at a concentration of 20-200 mg/L total organic carbon (TOC) for 35 days. As reference substance, sodium benzoate (0.069 g/400 mL) has been used. The percentage biodegradation is calculated from the total carbon transformed to biogas and DIC and the measured or calculated amount of carbon added as test item.

Referring to the test substance, 8% degradation has been determined after 1 day, followed by 51% after 8 days, 57% after 15 days, 61% after 22 days and 100% after 35 days. With regard to the reference substance, 6% degradation was determined after 8 days and 100% after 35 days.